1. Field of the Invention
This invention relates to upright vacuum cleaners and, more particularly, to upright vacuum cleaners incorporating a cyclone separator in a filter bag-type system.
2. State of the Prior Art
Upright vacuum cleaners include a handle mounted to a base and pivotable between an inclined use position and a generally vertical storage position. Such an upright vacuum cleaner is disclosed in commonly owned U.S. patent application Ser. No. 09/487,407, filed Jan. 19, 2000, now U.S. Pat. No. 6,256,833 issued Jul. 10, 2001. The disclosed upright vacuum cleaner includes a suction nozzle in the base and an agitation brush in the suction nozzle, the suction nozzle being fluidly connected to a suction source and a filter bag enclosure mounted to the handle of the cleaner. Soil from a surface being cleaned is entrained in an airflow from the suction nozzle and transported to the filter bag enclosure for deposit in a semi-permeable filter bag, as is well known in the art. A filter bag is generally disposable, and requires frequent replacement when it becomes fill. The effectiveness of some vacuum cleaners decreases prior to the filter bag becoming full, as fine particles trapped by the filter bag degrade its permeability and cause a loss of suction deliverable to the suction nozzle.
Vacuum cleaners using a cyclone separator are known in the art, and have the advantage of not requiring replacement of the disposable, non-reusable, filter bag. However, in order to match the dirt capacity of a filter bag-type vacuum cleaner, the cyclone-type vacuum cleaner must be larger to accommodate the generally cylindrical cyclone separation chamber. A side effect of increasing the diameter of the cyclone chamber is a decrease in the available efficiency of dirt separation; the power available to the vacuum cleaner can generate a finite airflow, and as the cyclone chamber increases in size, that finite airflow results in a lower velocity within the cyclone chamber. This lower velocity adversely affects the efficiency of the cyclone separator. The large dirt reservoir is also cumbersome to handle while still requiring frequent emptying to avoid re-entrainment of collected dirt into the suction airstream. Decreasing the size of the cyclone chamber could increase its efficiency and ease of handling, but at the cost of further decreasing its capacity to hold dirt when compared to the filter bag-type cleaner.
U.S. Pat. No. 6,146,434 issued Nov. 14, 2000, to Scalfani et al. discloses a stick vacuum cleaner having a cyclonic dirt cup assembly and a filter element in the suction plenum of the suction motor. The “stick” vacuum disclosed is limited by weight in the strength of suction motor it can accommodate. Further, the lesser efficiency of a larger cyclone, combined with a large, undifferentiated exhaust opening from the cyclone directly into the filter element, will lead to rapid degradation of filter permeability, and will require frequent replacement of the filter element.
It would be advantageous to provide a vacuum cleaner incorporating the advantage of an efficient cyclone separator that is easy to empty and restricts passage of dirt particles in a working airflow, with the supplemental filtering and dirt-carrying capacity of a filter bag.